New Insights into Micropollutant Abatement in Ammonia-Containing Water by the UV/Breakpoint Chlorination Process

Ultraviolet (UV)/chlorine processes are emerging advanced oxidation (AOPs) for micropollutant abatement. When excessive chlorine (Cl/N mass ratio of >7.6) is applied to ammonia-containing water yield free residual the UV/free AOP, AOP becomes UV/breakpoint chlorination. This study investigated degradation by and radical yields from chlorination under various conditions using benzoic acid (BA) nitrobenzene (NB) as representative micropollutants probes. Two stages were observed. During stage I, BA NB rapidly degraded; this was attributed reactive species generated breakpoint (Rbrk) UV photolysis chlor(am)ines intermediates/products (Rpho). II, followed pseudo-first-order kinetics, unknown irreducible residuals produced greatly contributed generating species, in addition chlorine. At pH 7 an ammonia concentration 1 mg/L N, optimum dosage existed at 9.6 Cl2 due strong scavenging The findings demonstrate that a promising approach degrading refractory real-world applications.